Chapter 5. KVM Paravirtualized (virtio) Drivers

Procedure 5.1. Using KVM virtio drivers for existing devices

1. Ensure that you have installed the appropriate driver (viostor), before continuing with this procedure.
2. Run the virsh edit guestname command as root to edit the XML configuration file for your device. For example, virsh edit guest1. The configuration files are located in the /etc/libvirt/qemu/ directory.
3. Below is a file-based block device using the virtualized IDE driver. This is a typical entry for a virtual machine not using the virtio drivers.

   <disk type='file' device='disk'>
   	 ...
      <source file='/var/lib/libvirt/images/disk1.img'/>
      <target dev='hda' bus='ide'/>
   	 <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
   </disk>

4. Change the entry to use the virtio device by modifying the bus= entry to virtio. Note that if the disk was previously IDE, it has a target similar to hda, hdb, or hdc. When changing to bus=virtio the target needs to be changed to vda, vdb, or vdc accordingly.

   <disk type='file' device='disk'>
      ...
      <source file='/var/lib/libvirt/images/disk1.img'/>
      <target dev='vda' bus='virtio'/>
   	 <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
   </disk>

5. Remove the address tag inside the disk tags. This must be done for this procedure to work. Libvirt will regenerate the address tag appropriately the next time the virtual machine is started.